This invention relates to a disc brake for use in a brake system wherein first and second ears on opposite sides of a caliper hold corresponding first and second guide pins substantially perpendicular to a rotor to oppose caliper twisting moments developed on engagement of friction members with a rotor and wherein a substantially constant cumulative bearing length of engagement between the first and second guide pins and a support member may be maintained with changes in thickness of the thickness of the first and second friction members caused by wear engagement with the rotor.
Disc brakes wherein two support members, which are spaced apart from each other and slidably guide first and second friction pads on first and guide pins during a brake application are known in the prior art. The following U.S. Pat. Nos. 4,958,703; 5,749,445; 5,810,112; 5,819,884 5,934,416 may be considered to be typical of such disc brakes. In these disc brakes, the first and second guide pins are correspondingly retained in first and second bores in a support member that is fixed to the frame of a vehicle. The first and second guide pins move in the first and second bores as the thickness of the first and second friction pads decrease during the engagement with a rotor and as a result the bearing engagement surface correspondingly decreases. Under some circumstances as the bearing surface decreases, the resistance to a moment caused by the engagement of the friction pads with the rotor may cause twisting of the caliper such that the wear surface of the friction pads is not entirely uniform. This non-uniform wear may result in a need to replace the friction pad before its projected usefulness life is achieved.
A primary object of the present invention is to provide a disc brake wherein the effect of a caliper twisting moment caused on engagement of friction pads with a rotor is essentially reduced or eliminated while the cumulative bearing length of engagement between the first and second guide pins and a support member remain substantially constant with changes in thickness of the first and second friction pads caused by wear engagement with a rotor.
In more particular detail, the disc brake has a support member secured to a vehicle with a first guide pin located in a first bore and a second guide pin located in a second bore. The first and second bores are, complimentary and define first and second bearing surfaces for aligning a caliper over a rotor associated with a wheel of the vehicle. The caliper is a uniform housing with an actuation section located on a first side of the rotor and connected by a bridge to an arm located on a second side of the rotor. The actuation section has a bore therein for retaining a piston to define an actuation chamber. A first friction member is connected to the piston and a second friction member connected to the arm. To effect a brake application pressurized fluid is presented to the actuation chamber which acts on the piston and actuation section to develop a force for moving the first and second friction members into engagement with the rotor to effect a brake application. The caliper is characterized by a first ear that extends from the actuation section and a second ear that extends from the arm. The first guide pin engages the first ear and is located in the first bore while the second guide pin engages the second ear and is located in the second bore. The engagement of the first and second pins with the first and second pins resists caliper twisting moments caused by off-set forces between friction members on engagement with the rotor to retain the corresponding engagement surfaces of the first and second friction members in a parallel planes with the rotor. With changes in the thickness of the first and second friction member caused by wear engagement with the rotor, the arm moves toward the support member and correspondingly the second pin moves into the second bore to increase its bearing length while the actuation section
An advantage of the disc brake results in a uniform wear of a thickness of a friction member on engagement with a rotor.
An object of this invention is to provide a disc brake with a guide pins whereby a cumulative bearing length remains constant with a decrease in a thickness of friction pads caused by wear.